This invention generally relates to thermoplastics and articles formed therefrom. More particularly, the invention relates to block copolymers and their preparation from macrocyclic oligoesters and dihydroxyl-functionalized polymers.
Linear polyesters such as poly(alkylene terephthalate) are generally known and commercially available where the alkylene typically has 2 to 8 carbon atoms. Linear polyesters have many valuable characteristics including strength, toughness, high gloss, and solvent resistance. Linear polyesters are conventionally prepared by the reaction of a diol with a dicarboxylic acid or its functional derivative, typically a diacid halide or ester. Linear polyesters may be fabricated into articles of manufacture by a number of known techniques including extrusion, compression molding, and injection molding.
Recently, macrocyclic oligoesters were developed which are precursors to linear polyesters. Macrocyclic oligoesters exhibit low melt viscosity, which can be advantageous in some applications. Furthermore, certain macrocyclic oligoesters melt and polymerize at temperatures well below the melting point of the resulting polymer. Upon melting and in the presence of an appropriate catalyst, polymerization and crystallization can occur virtually isothermally.
Block copolymers such as copolyester elastomers are known that are typically prepared from short-chain aliphatic diols, aromatic diacids, and polyalkylene ether diols. For example, one commercial product is a copolymer of 1,4-butanediol, dimethyl terephthalate, and polytetramethylene ether glycol. This copolymer is prepared via polycondensation reactions in two steps at high temperature and high vacuum. The polycondensation reactions may take tens of hours or even days. In addition, the high temperature (about 250xc2x0 C.) that is necessary for the polycondensation reactions causes significant degradation of polytetramethylene ether glycol. Furthermore, the molecular weight of polytetramethylene ether glycol is limited to 1000 or less in order to minimize significant phase separation during the polycondensation reaction.
Block copolymers of high molecular weight have been prepared from macrocyclic oligoesters and dihydroxyl-functionalized polymers at an elevated temperature in the presence of a transesterification catalyst. The methods of the invention allow the design and control of the elasticity, the crystallinity, the ductility, and the molecular weight of the resulting block copolymers, while retaining other desirable properties of polyesters prepared from macrocyclic oligoesters as precursors.
In one aspect, the invention generally features a method for making a block copolymer. In one embodiment, the method includes the step of contacting a macrocyclic oligoester and a dihydroxyl-functionalized polymer at an elevated temperature in the presence of a transesterification catalyst. The co-polymerization produces a block copolymer of polyester (derived from the macrocyclic oligoester) and the dihydroxyl-functionalized polymer. The macrocyclic oligoester has a structural repeat unit of formula (I): 
wherein R is an alkylene, a cycloalkylene, or a mono- or polyoxyalkylene group; and A is a divalent aromatic or alicyclic group.
In another aspect, the invention features a method for making high molecular weight block copolymer. In one embodiment, the method includes the steps of: (a) contacting a macrocyclic oligoester and a dihydroxyl-functionalized polymer at an elevated temperature in the presence of a transesterification catalyst to produce a block copolymer of polyester and the dihydroxyl-functionalized polymer; and (b) heating the block copolymer in the presence of a chain extension agent. The chain extension step results in a higher molecular weight block copolymer of polyester and the dihydroxyl-functionalized polymer.
In yet another aspect, the invention features another method for making high molecular weight block copolymer. In one embodiment, the method includes the steps of (a) heating a dihydroxyl-functionalized polymer with a diester in the presence of a transesterification catalyst, thereby producing a chain-extended dihydroxyl-functionalized polymer; and (b) contacting the chain-extended dihydroxyl-functionalized polymer with a macrocyclic oligoester at an elevated temperature in the presence of a transesterification catalyst. The co-polymerization produces a block copolymer of polyester and the chain-extended dihydroxyl-functionalized polymer.
In yet another aspect, the invention generally features a method for extending the chain length of a polyester polymer. In one embodiment, the method includes the step of contacting the polyester polymer and a chain extension agent at an elevated temperature.
In yet another aspect, the invention features a block copolymer. The block copolymer has at least two block units. The first block unit has, within its polymeric backbone, at least one first structural unit of formula (II) 
where R is an alkylene, or a cycloalkylene or a mono- or polyoxyalkylene group, and A is a divalent aromatic or alicyclic group. The second block unit has, within its polymeric backbone, at least one second structural unit of formula (III)
xe2x80x94Bxe2x80x94xe2x80x83xe2x80x83(III)
where B is an alkylene, or a cycloalkylene or a mono- or polyoxyalkylene group. One or more of the carbon atoms in B may be replaced with an oxygen atom, a nitrogen atom, or a sulfur atom.
The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and claims.
In an embodiment according to the present invention, high molecular weight block copolymers can be prepared from macrocyclic oligoesters and dihydroxyl-functionalized polymers at an elevated temperature in the presence of a transesterification catalyst.
Definitions
The following general definitions may be helpful in understanding the various terms and expressions used in this specification.
As used herein, a xe2x80x9cmacrocyclicxe2x80x9d molecule means a cyclic molecule having at least one ring within its molecular structure that contains 8 or more atoms covalently connected to form the ring.
As used herein, an xe2x80x9coligomerxe2x80x9d means a molecule that contains 2 or more identifiable structural repeat units of the same or different formula.
As used herein, an xe2x80x9coligoesterxe2x80x9d means a molecule that contains 2 or more identifiable ester functional repeat units of the same or different formula.
As used herein, a xe2x80x9cmacrocyclic oligoesterxe2x80x9d means a macrocyclic oligomer containing 2 or more identifiable ester functional repeat units of the same or different formula. A macrocyclic oligoester typically refers to multiple molecules of one specific formula having varying ring sizes. However, a macrocyclic oligoester may also include multiple molecules of different formulae having varying numbers of the same or different structural repeat units. A macrocyclic oligoester may be a co-oligoester or multi-oligoester, i.e., an oligoester having two or more different structural repeat units having an ester functionality within one cyclic molecule.
As used herein, a xe2x80x9cdihydroxyl-functionalized polymerxe2x80x9d means a polymer having at least two hydroxyl functional groups. Typically, the at least two hydroxyl functional groups are at the ends of a polymer chain. However, the polymer may be branched and each of the two or more of branches of the polymer chain may have a hydroxyl functionalized end.
As used herein, xe2x80x9can alkylene groupxe2x80x9d means xe2x80x94CnH2nxe2x80x94, where nxe2x89xa72.
As used herein, xe2x80x9ca cycloalkylene groupxe2x80x9d means a cyclic alkylene group, xe2x80x94CnH2nxe2x88x92xxe2x88x92, where x represents the number of H""s replaced by cyclization(s).
As used herein, xe2x80x9ca mono- or polyoxyalkylene groupxe2x80x9d means [xe2x80x94(CH2)mxe2x80x94Oxe2x80x94]nxe2x80x94(CH2)mxe2x80x94, wherein m is an integer greater than 1 and n is an integer greater than 0.
As used herein, xe2x80x9ca divalent aromatic groupxe2x80x9d means an aromatic group with links to other parts of the macrocyclic molecule. For example, a divalent aromatic group may include a meta- or para- linked monocyclic aromatic group (e.g., benzene).
As used herein, xe2x80x9can alicyclic groupxe2x80x9d means a non-aromatic hydrocarbon group containing a cyclic structure therein.
As used herein, a xe2x80x9cblock copolymerxe2x80x9d means a copolymer having segments of two or more polymers linked to one another. A block copolymer has constitutionally different structural units. Adjacent segments (i.e., blocks) contain structural units derived from different characteristic species of monomer or from structural repeat units with different composition or sequence distribution.
As used herein, a xe2x80x9cchain extension agentxe2x80x9d means an agent which facilitates extension of a polymer (or oligomer) chain.
As used herein, xe2x80x9ca polyester polymer compositexe2x80x9d means a polyester polymer that is associated with another substrate such as a fibrous or particulate material. Illustrative examples of particulate material are chopped fibers, glass microspheres, and crushed stone. Certain fillers and additives thus can be used to prepare polyester polymer composites. A fibrous material means a more continuous substrate, e.g., fiberglass, ceramic fibers, carbon fibers or organic polymers such as aramid fibers.
Block Copolymers
High molecular weight copolymers have been prepared from macrocyclic oligoesters and dihydroxyl-functionalized polymers at an elevated temperature in the presence of a transesterification catalyst.
In one aspect, the invention generally features a method for making a block copolymer. In one embodiment, the method includes the step of contacting a macrocyclic oligoester and a dihydroxyl-functionalized polymer at an elevated temperature in the presence of a transesterification catalyst. The co-polymerization produces a block copolymer of polyester and the dihydroxyl-functionalized polymer. The macrocyclic oligoester has a structural repeat unit of formula (I): 
wherein R is an alkylene, a cycloalkylene, or a mono- or polyoxyalkylene group; and A is a divalent aromatic or alicyclic group.
The co-polymerization reaction between a macrocyclic polyester oligomer and a dihydroxyl-functionalized polymer is typically completed within minutes. The duration of the co-polymerization reaction depends on many factors including the molar ratio of the macrocyclic oligoester to the di-hydroxyl-functionalized polymer, the molar ratio of the catalyst to the macrocylic oligoester and the di-hydroxyl-functionalized polymer, the temperature at which the co-polymerization reaction is carried out, the desired molecular weight of the resulting block copolymer, and the choice of solvent and other reaction conditions. The co-polymerization reaction is preferably conducted under an inert environment, such as under nitrogen or argon, or under a vacuum.
The weight ratio of the dihydroxyl-functionalized polymer to macrocyclic oligoester can vary from about 0.01 to 10. In one embodiment, the molar ratio of cyclic ester to macrocyclic oligoester is between about 0.01 to about 0.1. In another embodiment, the molar ratio of cyclic ester to macrocyclic oligoester is between about 0.1 to about 1.0. In yet another embodiment, the molar ratio of cyclic ester to macrocyclic oligoester is between about 1.0 to about 5.0. In yet another embodiment, the molar ratio of cyclic ester to macrocyclic oligoester is between about 5.0 to about 10.
The molar ratio of the transesterification catalyst to the macrocyclic oligoester can range from about 0.01 to about 10 mole percent. In one embodiment, the molar ratio of the catalyst to the macrocyclic oligoester is from about 0.01 to about 0.1 mole percent. In another embodiment, the molar ratio of the catalyst to the macrocyclic oligoester is from about 0.1 to about 1 mole percent. In yet another embodiment, the molar ratio of the catalyst to the macrocyclic oligoester is from about 1 to about 10 mole percent.
The co-polymerization reaction between the macrocyclic oligoester and the dihydroxyl-functionalized polymer is carried out at an elevated temperature. In one embodiment, the temperature at which the co-polymerization is conducted ranges from about 130xc2x0 C. to about 300xc2x0 C. In yet another embodiment, the temperature at which the co-polymerization is conducted ranges from about 150xc2x0 C. to about 260xc2x0 C. In yet another embodiment, the temperature at which the co-polymerization is conducted ranges from about 170xc2x0 C. to about 210xc2x0 C. In yet another embodiment, the temperature at which the co-polymerization is conducted ranges from about 180xc2x0 C. to about 190xc2x0 C.
Yields of block copolymer depend on, among other factors, the precursor macrocyclic oligoester(s) used, the dihydroxyl-functionalized polymer(s) used, the polymerization catalyst(s) used, the reaction time, the reaction conditions, the presence or absence of chain-extension agent(s), and the work-up procedure. Typical yields range from about 90% to about 98% of the macrocyclic oligoester used. In one embodiment, the yield is within a range from about 92% to about 95%.
Block copolymers may be designed and prepared according to methods of the invention to achieve desired elasticity, crystallinity, and/or ductility. Block copolymers having a high weight percentage of the dihydroxyl-functionalized polymer content (e.g., polytetramethylene ether glycol), for example, exhibit an increased toughness and become elastomaric. Similar block copolymers having a low weight percentage of the dihydroxyl-functionalized polymer content exhibit an increased elasticity.
The co-polymerization reaction may be carried out with or without a solvent. A solvent may be used to dissolve one or more of the reactants and/or to mix the reactants. A solvent may also be used as a medium in which the reaction is carried out. Illustrative solvents that may be used include high-boiling compounds such as o-dichlorobenzene and meta-terphenyl. In another embodiment, no solvent is used in the co-polymerization reaction.
In one embodiment, the above method further includes a step of heating the block copolymer in the presence of a chain extension agent, thereby producing a block copolymer with a higher molecular weight. The chain extension agent may be any material that facilitates chain extension of the block copolymer including, for example, diacid chlorides, diisocyanates, and diepoxides. In one embodiment, 4,4xe2x80x2-methylenebis(phenyl isocyanate) is used as the chain extension agent. In another embodiment, terephthaloyl chloride is used as the chain extension agent. In yet another embodiment, a tin or a titanate compound is used as a chain extension agent. In yet another embodiment, two or more of these and other chain extension agents may be used together or sequentially.
The step of heating the block copolymer in the presence of a chain extension agent may be conducted at a temperature within a range from about 130xc2x0 C. to about 300xc2x0 C. In one embodiment, the step of heating the block copolymer in the presence of a chain extension agent is conducted at a temperature within a range from about 150xc2x0 C. to about 260xc2x0 C. In another embodiment, the step of heating the block copolymer in the presence of a chain extension agent is conducted at a temperature within a range from about 170xc2x0 C. to about 210xc2x0 C. In yet another embodiment, the step of heating the block copolymer in the presence of a chain extension agent is conducted at a temperature within a range from about 180xc2x0 C. to about 190xc2x0 C.
One of the reactants employed in various embodiments of the invention to prepare block copolymers is a macrocyclic oligoester. Many different macrocyclic oligoesters readily can be made and are useful in the practice of this invention. Thus, depending on the desired properties of the final block copolymer product, the appropriate macrocyclic oligoester(s) can be selected for use in its manufacture.
Macrocyclic oligoesters that may be employed in this invention include, but are not limited to, macrocyclic poly(alkylene dicarboxylate) oligomers having a structural repeat unit of the formula: 
wherein R is an alkylene, a cycloalkylene, or a mono- or polyoxyalkylene group; and A is a divalent aromatic or alicyclic group.
Preferred macrocyclic oligoesters are macrocyclic oligoesters of 1,4-butylene terephthalate, 1,3-propylene terephthalate, 1,4-cyclohexylenedimethylene terephthalate, ethylene terephthalate, and 1,2-ethylene 2,6-naphthalenedicarboxylate, and macrocyclic co-oligoesters comprising two or more of the above structural repeat units.
Synthesis of the macrocyclic oligoesters may be achieved by contacting at least one diol of the formula HOxe2x80x94Rxe2x80x94OH with at least one diacid chloride of the formula: 
where R and A are as defined above. The reaction typically is conducted in the presence of at least one amine that has substantially no steric hindrance around the basic nitrogen atom. An illustrative example of such amines is 1,4-diazabicyclo[2.2.2]octane (DABCO). The reaction usually is conducted under substantially anhydrous conditions in a substantially water invincible organic solvent such as methylene chloride. The temperature of the reaction typically is within the range of from about xe2x88x9225xc2x0 C. to about 25xc2x0 C. See, e.g., U.S. Pat. No. 5,039,783 to Brunelle et al.
Macrocyclic oligoesters also can be prepared via the condensation of a diacid chloride with at least one bis(hydroxyalkyl) ester such as bis(4-hydroxybutyl) terephthalate in the presence of a highly unhindered amine or a mixture thereof with at least one other tertiary amine such as triethylamine. The condensation reaction is conducted in a substantially inert organic solvent such as methylene chloride, chlorobenzene, or a mixture thereof. See, e.g., U.S. Pat. No. 5,231,161 to Brunelle et al.
Another method for preparing macrocyclic oligoesters or macrocyclic co-oligoesters is the depolymerization of linear polyester polymers in the presence of an organotin or titanate compound. In this method, linear polyesters are converted to macrocyclic oligoesters by heating a mixture of linear polyesters, an organic solvent, and a transesterification catalyst such as a tin or titanium compound. The solvents used, such as o-xylene and o-dichlorobenzene, usually are substantially free of oxygen and water. See, e.g., U.S. Pat. Nos. 5,407,984 to Brunelle et al. and 5,668,186 to Brunelle et al.
It is also within the scope of the invention to employ macrocyclic co-oligoesters to produce block copolymers. Therefore, unless otherwise stated, an embodiment of a composition, article, or methods that refers to macrocyclic oligoesters also includes embodiments utilizing macrocyclic co-oligoesters.
Dihydroxyl-functionalized polymers employed in various embodiments of the invention include any dihydroxyl-functionalized polymer that reacts with a macrocyclic oligoester to form a block copolymer under transesterification conditions. Illustrative examples of classes of dihydroxyl-functionalized polymers include polyethylene ether glycols, polypropylene ether glycols, polytetramethylene ether glycols, polyolefin diols, polycaprolactone diols, polyperfluoroether diols, and polysiloxane diols. Illustrative examples of dihydroxyl-functionalized polymers include dihydroxyl-functionalized polyethylene terephthalate and dihydroxyl-functionalized polybutylene terephthalate. The molecular weight of the dihydroxyl-functionalized polymer used may be, but is not limited to, about 500 to about 100,000. In one embodiment, the molecular weight of the dihydroxyl-functionalized polymer used is within a range from about 500 to about 50,000. In another embodiment, the molecular weight of the dihydroxyl-functionalized polymer used is within a range from about 500 to about 10,000.
Catalysts employed in the invention are those that are capable of catalyzing a transesterification polymerization of a macrocyclic oligoester with a dihydroxyl-functionalized polymer. One or more catalysts may be used together or sequentially. As with state-of-the-art processes for polymerizing macrocyclic oligoesters, organotin and organotitanate compounds are the preferred catalysts, although other catalysts may be used.
Illustrative examples of classes of tin compounds that may be used in the invention include monoalkyltin(IV) hydroxide oxides, monoalkyltin(IV) chloride dihydroxides, dialkyltin(IV) oxides, bistrialkyltin(IV) oxides, monoalkyltin(IV) trisalkoxides, dialkyltin(IV) dialkoxides, trialkyltin(IV) alkoxides, tin compounds having the formula (IV): 
and tin compounds having the formula (V): 
wherein R2 is a C1-4 primary alkyl group, and R3 is C1-10 alkyl group.
Specific examples of organotin compounds that may be used in this invention include dibutyltin dioxide, 1,1,6,6-tetra-n-butyl-1,6-distanna-2,5,7,10-tetraoxacyclodecane, n-butyltin(IV) chloride dihydroxide, di-n-butyltin(IV) oxide, dibutyltin dioxide, di-n-octyltin oxide, n-butyltin tri-n-butoxide, di-n-butyltin(IV) di-n-butoxide, 2,2-di-n-butyl-2-stanna-1,3-dioxacycloheptane, and tributyltin ethoxide. See, e.g., U.S. Pat. No. 5,348,985 to Pearce et al. In addition, tin catalysts described in commonly owned U.S. Ser. No. 09/754,943 (incorporated by reference below) may be used in the polymerization reaction.
Titanate compounds that may be used in the invention include titanate compounds described in commonly owned U.S. Ser. No. 09/754,943 (incorporated by reference below). Illustrative examples include tetraalkyl titanates (e.g., tetra(2-ethylhexyl) titanate, tetraisopropyl titanate, and tetrabutyl titanate), isopropyl titanate, titanate tetraalkoxide. Other illustrative examples include (a) titanate compounds having the formula (VI): 
wherein each R4 is independently an alkyl group, or the two R4 groups taken together form a divalent aliphatic hydrocarbon group; R5 is a C2-10 divalent or trivalent aliphatic hydrocarbon group; R6 is a methylene or ethylene group; and n is 0 or 1, (b) titanate ester compounds having at least one moiety of the formula (VII): 
wherein each R7 is independently a C2-3 alkylene group; Z is O or N; R8 is a C1-6 alkyl group or unsubstituted or substituted phenyl group; provided when Z is 0, m=n=0, and when Z is N, m=0 or 1 and m+n =1, and (c) titanate ester compounds having at least one moiety of the formula (VIII): 
wherein each R9 is independently a C2-6 alkylene group; and q is 0 or 1.
The resulting high molecular weight block copolymer of polyester and the dihydroxyl-functionalized polymer may have a molecular weight within a range from about 10,000 to 300,000. In one embodiment, the molecular weight of the block copolymer of polyester and the dihydroxyl-functionalized polymer is within a range from about 10,000 to about 70,000. In another embodiment, the molecular weight of the block copolymer of polyester and the dihydroxyl-functionalized polymer is within a range from about 70,000 to about 150,000. In yet another embodiment, the molecular weight of the block copolymer of polyester and the dihydroxyl-functionalized polymer is within a range from about 150,000 to about 300,000.
In another aspect, the invention relates to a method for making high molecular weight block copolymer comprising the steps of contacting a macrocyclic oligoester and a dihydroxyl-functionalized polymer at an elevated temperature in the presence of a transesterification catalyst to produce a block copolymer of polyester and the dihydroxyl-functionalized polymer; and heating the block copolymer in the presence of a chain extension agent, thereby producing a high molecular weight block copolymer of polyester and the dihydroxyl-functionalized polymer.
In one embodiment, a high molecular weight block copolymer is produced after heating the block copolymer of polyester and the dihydroxyl-functionalized polymer produced in the first step in the presence of a chain extension agent. The step of heating the block copolymer in the presence of a chain extension agent is conducted at a temperature within a range from about 130xc2x0 C. to about 300xc2x0 C. In one embodiment, the step of heating the block copolymer in the presence of a chain extension agent is conducted at a temperature within a range from about 150xc2x0 C. to about 260xc2x0 C. In another embodiment, the step of heating the block copolymer in the presence of a chain extension agent is conducted at a temperature within a range from about 170xc2x0 C. to about 210xc2x0 C. In yet another embodiment, the step of heating the block copolymer in the presence of a chain extension agent is conducted at a temperature within a range from about 180xc2x0 C. to about 190xc2x0 C.
In yet another aspect, the invention features a block copolymer. The block copolymer contains at least a first block unit and a second block unit. The first block unit has, within its polymeric backbone, at least one structural unit of formula (II) 
where R is an alkylene, or a cycloalkylene or a mono- or polyoxyalkylene group, and A is a divalent aromatic or alicyclic group. The second block unit has, within its polymeric backbone, at least one second structural unit of formula (III)
xe2x80x94Bxe2x80x94xe2x80x83xe2x80x83(III)
where B is an alkylene, or a cycloalkylene or a mono- or polyoxyalkylene group, one or more of the carbon atoms in B may be replaced with an oxygen atom, a nitrogen atom, or a sulfur atom.
Illustrative examples of block unit B include a polyethylene ether group, a polypropylene ether group, a polymethylene ether group, a polyolefin group, a polycaprolactone group, a polyperfluoroether diol, and a polysiloxane diol.
The block copolymer prepared from a macrocyclic oligoester and a di-hydroxyl-functionalized polymer may contain blocks derived from the macrocyclic oligoester, blocks derived from the dihydroxyl-functionalized polymer, and blocks derived from both the macrocyclic oligoester and the dihydroxyl-functionalized polymer. The length of the individual blocks and the sequence thereof can be designed to, serve particular applications.
In another aspect, the invention features a method for making high molecular weight block copolymer. In one embodiment, the method includes the steps of: (a) heating a dihydroxyl-functionalized polymer and a diester in the presence of a chain extension agent, thereby producing a chain-extended dihydroxyl-functionalized polymer; and (b) contacting the chain-extended dihydroxyl-functionalized polymer and a macrocyclic oligoester at an elevated temperature in the presence of a transesterification catalyst. The co-polymerization produces a block copolymer of polyester and the chain-extended dihydroxyl-functionalized polymer.
The diester that may be employed include dialkyl terephthalates such as dimethyl terephthalate and dimethyladipate.
The step of heating a dihydroxyl-functionalized polymer with a diester in the presence of a transesterification catalyst may be conducted at a temperature within a range from about 130xc2x0 C. to about 300xc2x0 C. In one embodiment, the step of heating a dihydroxyl-functionalized polymer with a diester in the presence of a transesterification catalyst is conducted at a temperature within a range from about 150xc2x0 C. to about 260xc2x0 C. In another embodiment, the step of heating a dihydroxyl-functionalized polymer with a diester in the presence of a transesterification catalyst is conducted at a temperature within a range from about 170xc2x0 C. to about 210xc2x0 C. In yet another embodiment, the step of heating a dihydroxyl-functionalized polymer with a diester in the presence of a transesterification catalyst is conducted at a temperature within a range from about 180xc2x0 C. to about 190xc2x0 C.
The amount of the diester used depends on factors including the desired molecular weight of the block copolymer to be produced. In one embodiment, the molar ratio of the diester to the dihydroxyl-functionalized polymer is within a range from about 0.1000 to about 0.9999.
The step of heating a dihydroxyl-functionalized polymer with a diester in the presence of a transesterification catalyst may be conducted under a vacuum. It may also be conducted in an inert environmental such as argon or nitrogen. The reaction is completed within about 5 minutes to about 45 minutes, and typically within about 30 minutes.
In another aspect, the invention features a method for extending the chain length of a polyester polymer. In one embodiment, the method includes the step of contacting the polyester polymer and a chain extension agent at an elevated temperature. The polyester polymer may be any polyester polymer including polybutylene terephthalate and polyethylene terephthalate.
The compositions and methods of the invention may be used to manufacture articles of various size and shape from various macrocyclic oligoesters and dihydroxyl-functionalized polymers. Exemplary articles that may be manufactured by the invention include without limitation automotive body panels and chassis components, bumper beams, aircraft wing skins, windmill blades, fluid storage tanks, tractor fenders, tennis rackets, golf shafts, windsurfing masts, toys, rods, tubes, bars stock, bicycle forks, and machine housings.
In the manufacture of an article, various types of fillers may be included. A filler often is included to achieve a desired purpose or property, and may be present in the resulting polyester polymer. For example, the purpose of the filler may be to provide stability, such as chemical, thermal or light stability, to the blend material or the polyester polymer product, and/or to increase the strength of the polyester polymer product. A filler also may provide or reduce color, provide weight or bulk to achieve a particular density, provide flame resistance (i.e., be a flame retardant), be a substitute for a more expensive material, facilitate processing, and/or provide other desirable properties as recognized by a skilled artisan. Illustrative examples of fillers are, among others, fumed silicate, titanium dioxide, calcium carbonate, chopped fibers, fly ash, glass microspheres, micro-balloons, crushed stone, nanoclay, linear polymers, and monomers. Fillers can be used to prepare polyester polymer composites.
Furthermore, in the manufacture of an article additional components (e.g., additives) may be added. Illustrative additives include colorants, pigments, magnetic materials, anti-oxidants, UV stabilizers, plasticizers, fire-retardants, lubricants, and mold releases.